The objective of this research proposal is to establish the substituent effect (NO2) on the mutagenicity and carcinogenicity of polynuclear aromatic hydrocarbons (PAH) and to determine whether the observed mutangenicity and carcinogenicity is due primarily to metabolic reduction of the nitro group, to ring epoxidation and diol epoxide formation, or to a contribution of both pathways. Representative examples are the known mutagenic environmental pollutants, 3-nitroperylene (3-NP and 6-nitrobenzo(a)pyrene (6-NBP). These direct acting mutagens are formed by exposure of PAH to low levels of NO2 in the atmosphere (approximately 1 ppm). These substances could represent a health hazard to humans exposed to small amounts. The proposed methods for metabolism studies will require the synthesis of 14C- and 3H-labeled 3-NP and 6-NBP. For isolation of metabolites, a combination of both high pressure liquid and thin layer chromatography will be employed. Structural elucidation of metabolites and their ultimate (or proximate) mutagens and carcinogens will be accomplished by means of spectral analysis and independent synthesis. Mutagenicity assays in S. typhimurium of 3-NP and 6-NBP and their metabolites will be performed. The influence of modifiers on their mutagenic activity will be examined. Both 3-NP and 6-NBP will be tested as tumor initiators on mouse skin and complete carcinogens in rat. Based on the carcinogenicity results, the likely ultimate carcinogen will be tested on mouse skin and in mutagenicity assays.